Antenna for space vehicle



g- 1969 E. I. PODRACZKY 3,460,148

ANTENNA FOR SPACE VEHICLE Filed Dec. 8, 1965 INVENTOR EMERIC IMREPODRACZKY United States Patent Olfice 3,460,148 Patented Aug. 5, 19693,460,148 ANTENNA FOR SPACE VEHICLE Emeric I. Podraczky, Bethesda, Md.,assignor to Communications Satellite Corporation, Washington, D.C. FiledDec. 8, 1965, Ser. No. 512,394 Int. Cl. H01q 1/28 US. Cl. 343-705 7.Claims This invention relates to an antenna and more particularly to adespun antenna for a spin-stabilized space satellite.

A spin-stabilized space satellite may be defined as one which is spunabout its axis to prevent change in its attitude with relation to theearth axis. Such attitude change would, in the absence of such aspinning arrangement, take place as a result of tumbling of thesatellite. One example of a spin-stabilized space satellite is thesynchronous satellite Syncom. Such a satellite is controllablypositioned in inertial space at a fixed point with relation to theearth. Its radial velocity is the same as that of the earth. In order toprevent tumbling or change in its attitude, a spin is imparted to thesatellite. The spin imparting means does not form a part of thisinvention but for background information this spinning is imparted bythe launch vehicle whereby when the satellite is injected into itsorbit, it is spinning or rotating about its axis at a speed which may bebetween 100 and 150 revolutions. This spin rate is of course definedwith relation to inertial space. Mechanically associated with thespin-stabilized space satellite is an antenna platform on which anantenna is mounted. This platform may be mounted to the satellite bymeans such as low-friction bearings. A suitable despinning motor mountedin the satellite and mechanically connected to the antenna may beprovided. This motor functions to prevent the antenna platform andtherefore the antenna from spinning at the spin rate of the satellite.In this context, the platform is identified as despun and the antennaidentified as operating in its despun mode. The radio frequency energypattern of the antenna is fixed with relation to the earth and has itsmajor axis fixed with relation to a point on the earth during the orbitof the satellite. The motor rotates the antenna platform in a directionopposite to the direction of rotation of the satellite at a speed equalto the rotational speed of the satellite less one revolution per orbit.

Since centrifugal forces are produced when an object is rotated relativeto inertial space, a despun platform oriented toward the earth issubject to relatively small centrifugal force. However, should it bedesirable for one reason or another to de-energize the despinning motoror should the despinning motor be de-energized inadvertently, thepresent invention provides means by which the energy pattern of theantenna switches from the despun mode (pencil beam) to an omni mode(toroidal beam). As previously stated, in the despun mode, the energypattern is a conventional lobe having its major axis directed toward theearth. In the omni mode, the pattern may be substantially doughnutshaped, that is, radiating substantially equally in the directionsperpendicular to the spin axis. While this omni mode results in someloss of power, it still defines a pattern which is useable forcommunication purposes. Were it otherwise, the de-energizing of thedespinning motor would result in the despun mode pattern persisting. Inthis event, a pattern is generated which has little or no utility forcommunication purposes.

The present invention relates to a fail safe antenna device forspin-stabilized space satellites in which the omni mode antenna energypattern is automatically achieved upon failure of the despinning motorby direction or by accident. This is done by taking advantage of thecentrifugal forces which are produced when the antenna rotates at thespin rate of the satellite due to despinning motor failure. Theseforces, acting upon the antenna device, change its physical arrangementand more particularly its reflector orientation to achieve the omni modetype of operation. Of course, de-energizing of the despinning motor willresult in the antenna platform and consequently the antenna withassociated reflectors rotating at the same speed as the satellite.

It is therefore an object of the present invention to provide a failsafe antenna device for a spin-stabilized space satellite having anormally despun section in which means are provided for producing anantenna RF energy pattern useable for communication purposes when thedespun section moves away from its normally biased active first positionto a passive second position as a result of deenergization of thedespinning arrangement using the centrifugal force developed by thenormally despun section rotating with the satellite to overcome saidbias. The active first position referred to in which the antenna arraynormally finds itself is of course the despun mode and the passivesecond position is of course the omni mode.

This, and other objects will become apparent from a more detaileddescription of the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view of a spin-stabilized satellite showingthe normally despun section including the antenna with reflector andassociated RF transparent cylinder, during a despun type of operation;

FIGURE 2 is similar to FIGURE 1, but representing the omni mode type ofoperation;

FIGURE 3 is similar to FIGURE 2, but illustrating a different type ofantenna reflector and transparent means;

FIGURE 4 is similar to FIGURE 3, but representing a despun mode type ofoperation;

FIGURE 5 is a perspective view of an antenna device but illustrating adiiferent type of reflector and transparent means operating in thedespun mode; and

FIGURE 6 is similar to FIGURE 5, but representing an omni mode type ofoperation.

Referring first to FIGURES 1 and 2, FIGURE 1 represents aspin-stabilized satellite 10 with antenna platform 11 mounted by bearingmeans 12 to the satellite. Mounted by spring-loaded hinges 16 to theplatform 11 are the metallic parabolic reflector 14 and the RFtransparent parabolic cylinder 15. The antenna is identified at 13. Theplatform 11 is mounted by some conventional means to a despinning motor(not shown) carried by the satellite. FIGURE 1 is illustrative of thedespun mode type of operation in which the members 14 and 15 are biasedby the springs 16 toward their active first position (the despun mode)and away from a passive second position (omni mode). Since thedespinning motor substantially prevents spinning of the platform withrelation to inertial space, the antenna device does not generate asignificant amount of centrifugal force. However, should the despinningmotor be de-energized, then the platform and associated antenna devicewill rotate along with the satellite 10 and the resultant centrifugalforces generated overcome the bias springs to move the members 14 and 15into the omni Inode type of operation shown in FIG- URE 2.

Of course it should be understood that springs are illustrative only.Any mechanical means performing a similar function may be employed. Infact, arrangements such as shown in FIGURES 3 through 6 may be employed.

Referring first to FIGURE 3, there is shown a satellite 10 operating inthe omni state. The antenna 13 is in this figure associated withflexible metallic wire reflectors 17 and flexible RF transparent wires18. The de-energizing of the despinning motor causes the antennaplatform and device to rotate with the satellite and to generatecentrifugal force whereby these Wires move from the despun mode as shownin FIGURE 4 to the omni mode shown in FIGURE 3.

FIGURES 5 and 6 illustrate respectively despun mode and omni mode typesof operation in which the reflectors are constituted of a plurality offlexible metallic petals :19 and the RF transparent means is in the formof a parabolic supporting cylinder 20.

With relation to all of the figures, the specific type of antenna array,reflector or RF transparent means is not critical to the invention. Asto the materials employed, the metallic reflector may be of any suitabletype commonly used in the art and the RF transparent means may be madeof Fiberglas. The flexible metallic wires referred to in FIGURES 3 and 4may be of conventional beryllium-copper type. This is also true inconnection with the flexible metallic petals shown in FIGURES 5 and 6.

The bearing means by which the antenna platform is mounted to thesatellite may be conventional. These bearings should be as frictionlessas possible. The despinning motor mounted within the satellite andconnected to the antenna platform may also be conventional and forms nopart of this invention.

The functioning of the RF transparent member is only for dynamicbalancing purposes.

What has been disclosed are various embodiments to the presentinvention. Other embodiments obvious to those skilled in the art fromthe teachings herein are contemplated to be within the spirit and thescope of the following claims.

What is claimed is:

1. A fail safe antenna device for a spin-stabilized space satellitehaving a normally despun section comprising: a radiator/collector membermounted on the despun section and wave reflector means mounted on thedespun section adjacent the radiator-collector member and biased towardan active first position and away from a passive second position wherebycentrifugal force overcomes the biasing to move the reflector means tothe passive second position whenever the normal despun section rotateswith the satellite.

2. A fail safe antenna device as claimed in claim 1 wherein saidnormally despun section comprises a platform means for carrying saidradiator/ collector member, and substantially frictionless bearing meansmounting said platform to said satellite.

3. A fail safe antenna device as claimed in claim 2 wherein said wavereflector means comprises a metallic parabolic cylinder.

4. A fail safe antenna device as claimed in claim 3 further includinghinge means connecting said platform and said wave reflector means.

5. A fail safe antenna device as claimed in claim 1 wherein said wavereflector means comprises a plurality of flexible metallic wires.

6. A fail safe antenna device as claimed in claim 1 wherein said wavereflector means comprises a plurality of flexible metallic petals.

7. A fail safe antenna device as claimed in claim 1 further including anRF transparent means mounted to said despun section adjacent saidradiator/collector oriented opposite to said wave reflector means.

References Cited UNITED STATES PATENTS 3,341,151 9/1967 Kampinsky 343705ELI LIEBERMAN, Primary Examiner U.S. Cl. X.R. 343724, 729

1. A FAIL SAFE ANTENNA DEVICE FOR A SPIN-STABLIZED SPACE STATELLITEHAVING A NORMALLY DESPUN SUCTION COMPRISING: A RADIATOR/COLLECTOR MEMBERMOUNTED ON THE DESPUN SECTION AND WAVE REFLECTOR MEANS MOUNTED ON THEDESPUN SECTION ADJACENT THE RADIATOR-COLLECTOR MEMBER AND BIASED TOWARDAN ACTIVE FIRST POSITION AND AWAY FROM A PASSIVE SECOND POSITION WHEREBYCENTRIFUGAL FORCE OVERCOMES THE BIASING TO MOVE THE REFLETOR MEANS TOTHE PASSIVE SECOND POSITION WHENEVER THE NORMAL DESPUN SECTION ROTATESWITH THE SATELLITE.